Field of the Invention
The present disclosure relates to an image processing apparatus, an image processing method, and a program, and more particularly, to a technique of displaying a projection image and a feature point of a 3-dimensional image.
Description of the Related Art
A maximum intensity projection method is generally used to visualize a tissue structure (a blood vessel or the like) in a 3-dimensional image captured using a medical imaging apparatus (X-ray CT, MRI, or the like). Japanese Patent Laid-Open No. 2013-70776 discloses a technique to generate a maximum intensity projection image such that for each pixel in a particular projection plane of a 3-dimensional image, a maximum value is acquired for voxel values of voxels of the 3-dimensional image on a line of sight crossing the pixel (that is, a maximum value on the line of sight is projected), and the acquired maximum value is employed as the value of the pixel. The maximum intensity projection image is also called a MIP (Maximum Intensity Projection) image.
In this technique, when a range in which voxels are projected is set across the projection plane (hereinafter, this range will be referred to as a projection range), only voxels in the projection range are subjected to the projection. A MIP image generated in a limited projection range as described above is generally called a slab MIP image. In this technique, a user sets the projection range such that a projection image is generated in a range of interest. In this technique, it is possible to more easily recognize continuity of a structure such as a blood vessel extending across a cross section than is possible in a case where only an image in a specified cross section is displayed.
In a case where a part to be observed is represented by voxel values lower than those in surrounding parts, a MinIP (Minimum Intensity Projection) image, in which not maximum values but minimum values are projected, is employed. Hereinafter, MIP images and MinP images are generically called projection images.
On the other hand, when locations of feature points of a 3-dimensional image are acquired, to make it possible for a user to recognize a distribution thereof, it is generally performed to display points such that 3-dimensional coordinates of feature points are projected onto a projection plane and the projected points are displayed. In particular, when a cross-section image of a 3-dimensional image is displayed, it is generally performed to project feature points such that the cross section is used as a projection plane, and feature points in a particular display range defined across the projection plane are projected onto the projection plane, and coordinates thereof are displayed such that they are superimposed on the cross-section image.
To display a distribution of feature points so as to be superimposed on a projection image, it is necessary to properly set a projection range of the projection image and a display range of feature points. However, in conventional image processing apparatuses, it is difficult to set the projection range and the display range, and thus it is difficult to display a distribution of feature points so as to be superimposed on the projection image.